1. Field of the Invention
This invention relates to a slidable support for a heavily loaded trailer jack post used to support the front end of a commercial, heavy duty trailer when not connected to a towing vehicle.
2. Description of the Related Art
Virtually all trailers, other than very light duty trailers, have a vertically extensible leg or jack post or a pair of such legs or posts and which are adapted to raise the front end of the trailer to an appropriate level to be engaged by a hitching device on a towing vehicle or to support the trailer when parked. In the case of a commercial freight trailer, the so-called fifth wheel on the towing vehicle, referred to as the tractor, includes a sliding engagement plate with an enlarged entrance slot for easy engagement by a pin attached to the trailer. This enlarged entrance slot compensates for a certain amount of misalignment between the tractor and the trailer and thus assists in slightly shifting the trailer relative to the tractor when the trailer is being connected to the tractor.
In another type of commercial application a trailer is attached to and towed by a full truck as different from a tractor. Light duty trailers of this type include those used for transporting boats, small garden tractors and the like. A typical example of a truck pulling a heavily loaded trailer is that of a utility company service truck towing a trailer on which utility poles, e.g. telephone or power poles, are transported. This type heavy duty trailer arrangement typically involves use of a hitching loop on the trailer and a mating hitching hook on the truck, which arrangement does not compensate at all for misalignment between the two vehicles. Essentially, the truck must be in perfect alignment in order to hitch the trailer to the truck.
Obviously, perfect alignment is not easily accomplished by backing a truck to a heavily loaded trailer. To correct for the common misalignment which occurs, the truck operator may attempt to move the heavily loaded trailer sideways manually. While this may be possible when the trailer has a dolly wheel on the bottom of a jack post which is supported on a hard and level surface, in other circumstances this movement cannot be done. The weight of a load of utility poles is great and even to the extent it may be balanced across the trailer's wheels still presents a formidable weight to move. A 20,000 pound gross load and a 5000 pound tongue load are normal loads for this type trailer. In a conventional widely employed type of heavy duty trailer, the jack post mounts a base or boot plate which remains secured to the lower end of the jack post during travel but contributes to the difficulty of lateral shifting of the front of the trailer during hitching. It is thus not uncommon for a truck operator to sustain a back injury while attempting to shift the front end of a heavily loaded trailer.
Practical slidable jack stands have been achieved which permit the lateral movement of a front portion of a relatively lightly loaded trailer such as a boat trailer. Such slidable jack stands suitable for relatively lightly loaded trailers are described in applicant's prior U.S. Pat. Nos. 5,009,444 and 5,195,769, the teachings of which are incorporated herein by reference. However, experience has revealed a need for an improved slidable jack stand for heavily loaded trailers and for a slidable jack stand which can be permanently attached to the trailer. The sliding jack support in the '769 patent, for example, requires the shifting force to be applied directly to the jack post being supported and has no means for enabling the lower end of the shifting lever to engage any of several positions all of which may be disadvantageous when shifting heavy loads. In addition, the sliding jack support of the '769 patent has to be repositioned in alignment with the jack leg each time the support is used.
It is therefore a primary object of this invention to improve on the slidable support of the '769 patent and to provide a slidable support for a heavily loaded trailer jack post so as to permit the lateral movement of the front portion of a relatively heavily loaded trailer in order to align the hitching mechanism to a towing truck without injury to the operator.
Other objects and advantages will be more fully apparent from the following disclosure and appended claims.